1. Filed of the Invention
The present invention relates to a resist composition which reacts upon irradiation with actinic rays or a radiation and thus changes in property and to a method of pattern formation with the composition. More particularly, the invention relates to a resist composition for use in the production of semiconductor devices, e.g., IC's, production of circuit boards for liquid crystals, thermal heads, etc., and other photofabrication processes, and to a method of pattern formation with the composition.
2. Description of the Related Art
A chemical amplification type resist composition is a material for pattern formation which functions by the following mechanism. Upon irradiation with a radiation such as, e.g., far ultraviolet rays, the composition generates an acid in the exposed areas and undergoes a reaction catalyzed by this acid. As a result, the composition comes to have a difference in solubility in a developing solution between the areas irradiated with the actinic radiation and the unirradiated areas to thereby form a pattern on the substrate.
In the case where a KrF excimer laser is employed as an exposure light source, a resin having a poly(hydroxystyrene) backbone, which shows reduced absorption mainly in a 248-nm region, is used as the main component. Because of this, the composition has high sensitivity and forms satisfactory patterns with high resolution. It is hence a better system as compared with the naphthoquinonediazide/novolak resin system heretofore in use.
On the other hand, in the case where a light source having a shorter wavelength, e.g., an ArF excimer laser (193 nm), is used as an exposure light source, even the chemical amplification type system has been insufficient because compounds having aromatic groups intrinsically show considerable absorption in a 193-nm region.
Because of this, resists for an ArF excimer laser which contain a resin having an alicyclic hydrocarbon structure have been developed.
With respect to the acid generator also, which is a major component of chemical amplification type resists, various compounds were found to be useful. In JP-A-10-39500 is described a resist composition containing a sulfonium salt having two or more anions in the molecule.
However, this resist composition was still insufficient in PEB temperature dependence and sensitivity, and improvements in these properties have been desired.